Top: Waterfall plot of stacked Lomb-Scargle periodograms. The right Y-axis indicates the middle MJD of each five-day slice, with the color gradient representing temporal progression. It illustrates the secular evolution of the spin frequency over the ∼56-day TESS observation baseline. Flanking the central period, two periods are observed that we identify as the beat periods between the orbital and spin periods (see Section 3.1). Middle: Evolution of the spin period as a function of time (MJD). The black points denote measurements from individual sliding windows, with 1σ uncertainties derived from 200-iteration Monte Carlo simulations integrated with an AR(p) red noise model. The red line represents a WLS linear fit, yielding a secular spin-down rate of Ṗ = 1.91 × 10⁻⁸±7.01 × 10⁻¹⁰ s/s, which represents a 20.9σ significance level over the constant hypothesis. The residuals of the linear period fit show no systematic trends or higher-order derivatives. Bottom: Pulse profile (50 bins) constructed via quadratic phase folding using the derived ephemeris ($\varphi (t)=f_0\mathrm{\Delta }t+\frac{1}{2}\dot{f}\mathrm{\Delta }{t}^2$). The phase-folded profile is dominated by a broad, quasi-sinusoidal modulation. The successful recovery of this complex structure across the full TESS baseline confirms high phase coherence (Q = 1/|Ṗ| ≈ 5.2 × 10⁷) and validates the quadratic timing correction (Ṗ = 1.91 × 10⁻⁸ s/s).